1. Field of the Invention
The present invention relates generally to an industrial gas turbine engine, and more specifically to a turbine rotor blade with integral platform and airfoil cooling.
2. Description of the Related Art Including Information Disclosed Under 37 CFR 1.97 and 1.98
A gas turbine engine includes a turbine with multiple rows or stages of rotor blades that react with a high temperature gas flow to produce mechanical power. In an industrial gas turbine (IGT) engine, this mechanical power is used to drive a compressor to supply pressurized air to the engine and to drive an electric generator for production of electrical power. The engine efficiency can be increased by passing a higher temperature gas flow into the turbine. However, the turbine inlet temperature is limited by the material properties of the turbine rotor blades and stator vanes, especially the first stage airfoils. Higher temperature resistant materials allow for turbine airfoils with increased operating temperatures.
Another way of allowing for higher turbine inlet temperatures is to provide more effective cooling of the airfoils. Either providing for more effective cooling of the cooling air flow through the airfoils, or by using less cooling air to provide the same amount of cooling would also increase the engine efficiency by wasting less compressed air. The compressed air used for internal cooling of the airfoils is bled off from the compressor and thus not used in the combustor to generate the hot gas flow.
Prior art turbine rotor blades have internal cooling circuits that include multiple pass serpentine flow cooling channels that flow either in an aft direction or a forward direction to provide high levels of cooling to the airfoil. Prior art serpentine circuits include 3-pass serpentines and 5-pass serpentines and are typically limited to these odd number of passes due to the source of the pressurized cooling air being supplied to the blade root section and that it is desirable to form the last leg of the serpentine with a flow direction towards the tip.